Created by kT

The first report on a synthetic polyelectrolyte, polyacrylic acid, was published by W. Kern (1939). Ten years later, Fuoss and Sadek reported the first complex between two synthetic, oppositely-charged polyelectrolytes. At the time, it seemed evident that “strong electrostatic interactions…would lead to mutual precipitation.” However, Michaels could not measure an enthalpy of complexation and concluded it was driven by entropy or the “escaping tendency of microions.” With more sensitive calorimetric measurements, complexation enthalpies were again ascribed to the coulombic forces assembling the component polyelectrolytes. In this talk I will show how polyelectrolyte coacervates, complexes and multilayers rely on the loss of counterions, an entropic driving force, to assemble. This overall driving force is moderated by an enthalpic contribution attributed to changes in the structure of water around counterion-compensated polyelectrolyte repeat units. The experimentally-determined relative ion concentrations within and external to a PEC are predicted by the Donnan equilibrium.